Regularity conditions in social welfare analysis can be seen as ways of making specific types of information "inadmissible" in welfare judgements: the evaluation is made invariant with respect to information of those types. In this sense, these conditions--often reflecting "principles" of judgement--serve also as informational constraints. In this lecture alternative approaches to social welfare evaluation are examined in this light. The analysis covers both Arrovian and Bergson--Samualsonian social welfare functions as well as principles underlying utilitarianism, Rawlsian conception of justice, notions of liberty and egality, and "historical" theories of rights and entitlements (e.g., Marx or Nozick.